Metamorphosis and embryogenesis are supported in all insects by special blood proteins that must be endocytosed, transferred to appropriate intracellular sites, and hydrolyzed to provide amino acids for development. The cellular and molecular mechanisms entailed are basic to the development, reproduction, and general protein trafficking in all insects, including those of medical and agricultural importance; the large lepidopteran that serves as a model system in this proposal is one of the species that are large enough to serve as convenient experimental material for these purposes. The experimental approaches would include: the use of monospecific antibodies to follow concentration changes of the normal and modified storage proteins in the blood, to look for the intracellular distributions of specific storage proteins, and to screen cDNA clones; the use of in vitro tissue incubations in assaying the ability of cells to endocytose and hydrolyze specific storage proteins; the extraction and characterization of the cell surface receptors responsible for stage-specific utilization; cDNA cloning and base sequencing to obtain amino acid sequences for at least two storage proteins--one an ancient protein that is present in all insects studied, and one an apparently newly evolved protein found so far in only one species. Cloned cDNA would be used as a probe for analyzing the nature of the recombinational events that are presumed to have given rise to the new protein.